Iran has won the diplomatic struggle over its nuclear program in Vienna. Its success was not due to United States negotiators' fecklessness as Republican critics and Prime Minister Netanyahu have been quick to assert.

Arguments against the pending nuclear deal with Iran -- from claiming that the deal is a capitulation to Iran to the notion that it is unacceptable to make a deal with a regime like that in Tehran -- have not sufficiently resonated with the public to kill the agreement. This has caused some disarray in the opposition camp. Indeed, if you are in that camp right now, it is reasonable to expect that the search is not for a new argument but for a game changing development: an event so powerful it shifts the momentum in Congress back to AIPAC, Netanyahu, Saudi Arabia and the other opponents of a nuclear deal. Arguably, a military confrontation between Israel and Hezbollah this summer could fit that bill.

Thirty-five years ago, the revolutionary government of Iran imprisoned my father and accused him of being a CIA agent. It was 1979. The revolution was in its infancy, and Islamic fundamentalism was about to foist itself on an unready world.

Favoring the pressure track of sanctions over a military intervention, it is not yet clear whether Obama is contemplating a grand bargain with Tehran, but the glimmer of an opportunity seems there. What is certain is that Rouhani represents Washington's best chance for peace.

The Iran issue is central to the right-wing mantra on Obama's foreign policy as consistently showing "weakness." But a diplomatic solution is a must -- and it would be fitting for Obama to cash in his chips after Tuesday and secure a nuclear deal.

How is it that the same candidate who advocated so strongly for using diplomacy with Iran ended up being the president that has implemented the most "crippling" sanctions to date -- and who made only one inchoate effort at negotiations?